A rolling bearing comprises an inner ring, an outer ring and several rolling bodies installed between these two rings. These rolling bodies can be balls, rollers or needles. In the meaning of the invention, a rolling bearing can be, for instance, a ball bearing, a roller bearing or a needle bearing.
In the field of rolling bearings, it is known to use a tachometer in order to determine the rotation speed of a member supported by a rolling bearing. For instance, truck lifts are equipped with electric motors to move upwardly or downwardly the forks of the truck. The position and speed of the forks must be controlled for safety reasons. In this context, it is known to use an instrumented rolling bearing assembly in order to support a rotating shaft of an electric motor with respect to a frame and to provide a variable-voltage regulator with some information with respect to a rotation parameter of the rotating shaft.
Such an instrumented rolling bearing assembly includes a sensor, in the form of an electronic component such as a Hall effect cell, and possibly some other electronic components for the treatment of the output signal of such a sensor. Such electronic components are subjected to an electromagnetic environment which is influenced, for instance, by the stator of the motor. Moreover, electronic fast transient phenomenons or “EFT” occur within such machines, such phenomenons being likely to damage the electronic components, in particular the sensor. For instance, in the case of a fork lift truck, the truck can charge electrostatically when moving on a plastic ground and, when it comes close to a grounded conducting element such as a metallic shelf, a fast discharge can occur which might damage the electronic components.
Such electromagnetic fast transient phenomenons or “EFT” have been taken into consideration so far by incorporating, next to the sensor or the electronic components of a rolling bearing assembly, an electronic filter to protect the electronic components of the rotation sensing means. Such a filter is bulky and increases the overall volume of the rolling bearing assembly to such an extent that it may prevent the rolling bearing assembly from being used in some circumstances. In some cases, the electronic filter has been reduced in size in order to fit with small diameters rolling bearing assemblies but, in such a case, the electronic filter is not really efficient.
On the other hand, it is known, e.g. from EP-A-1 211 500 to use an EMI filter as noise filter for eliminating high-frequency noise. Such a filter is not adapted to EFT and increases the overall volume of the bearing assembly.